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Case Study - The One Curious Case of Induction Motor

Today we are going to present a Case of Induction Motor, which might be rare in Industries. Hence, we want to share the experience, so that the problem faced by one Plant must not be faced by others or can be avoided.<br>

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Case Study - The One Curious Case of Induction Motor

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  1. ISO 9001:2015 ISO 45001:2015 (OH & S) Certified Company Case Study The One Curious Case of Induction Motor www.systemprotection.in +91-265-2225137

  2. TodaywearegoingtopresentaCaseof InductionMotor, whichmightberarein Industries. Hencewewanttosharethe experience, sothattheproblemfacedby onePlantmustnotbefacedbyothersor canbeavoided. WeagaincheckedtheMotorinDecoupled condition. Againeverythingwasnormal. Thenwethoughtthatitmightbedueto VFDproblem, asduringthesametimeNew VFDwasinstalledforspeedcontrol. Butno problemwasfoundinVFD. InaProcessPlant, therewasaFancalled DilutionAirFaninwhichtherewasaMotor of225KW, 415Volt, & 744RPM. Therewere2 suchFansineachofthe2unitsofKiln, makingittototalof4NosFanandhence4 Nosmotorwith1Nosspare (inStore) betweenallthefour. Alignmentwasdoneagainandtrialtaken inBothDecoupledandCoupledCondition. InDe-coupledMotorwasassmoothas Butter, butinCoupledConditionasMotor speedincreasesbeyond50% vibrationlevel startsincreasing Likealwaystherewastusslebetween departments (Electrical, Instrumentand Mechanical). "Thisisnotourfault". SoAfter5yearofrunningofplant, Maintenanceteamwantedtoreplacethe runningmotorwithsparemotor, available instoresincelast4 -5yearsandtakethe currentmotorforOver-Haulingduringa plannedshutdownof4days. SotoproveMechanicalwrongtheyput backtheoriginalmotorinPlace, Andtoour surpriseandshock, everythingwasback normalinbothDecoupledandCoupled condition, NoVibration, Nooverloading, smoothrunningoffan. Sotheycheckedthesparemotor completelyinworkshop, takenWinding Resistance, IRValueandTrialofMotorinNo LoadconditionandCheckedCurrentand VibrationinNo- Load. Everythingwasas smoothlikeButter. Everythingwaswithin permissiblelimits. Itwasastrangeproblemforeveryone. They checkedthemotorcompletelyafter removingrotorfromStator, checkedeach andeverythingbutfoundnothing. Then afterassemblingit, theytookthetrialagain. ButasusualmotorwasrunninggoodinNo- Loadcondition. SotheyreplaceditwithcurrentMotorand checkedalltheAlignmentreadingsafter beinginstalled, Alignmentreadingswere perfect. Nowtheplantwasstartednormallyandwe haveallthetimethoughtofevery possibility. Soafter3-4days, itstrikes suddenly, cantherebeawrongname plate? Ifyeshowtocheckit. Theychecked Resistance, Inductance, IRValueandNo Loadtrial; everythingwassamewiththatof Actualinstalledmotor. Sowhatwaswrong? Theonlythingwasn'tcheckwasRPM. As NormallyEngineersactuallybelievewhatis writtenontheMotorNamePlateis "Aline drawnontheRockorPattharKiLakeer" ButwhenMotorwascoupledwithFanand checkedwithVFDforTrial, Theyrunthefan for1hourin40 - 50% loadconditionsand everythingwasnormal. Duetocertainwork beingcarriedoutbymechanical, we couldn’ttakethespeedtomorethan50% Nowfiringofplantstartedafter2daysand after12hoursrequirementofDilutionAir fanarises. SowhentheFangoestoFull speedwith100% Damperopen, therewas heavyvibrationinFanandMotorboth. NowtheycheckedtheRPMfortheFirst timein7DaysandtheProblemwas identified. Themotorwasrunningat1000 RPMinsteadof750RPM. Andnowallthe Vibrationlevels, Damperpositionand Currentslevelproblemwereclear. TheVibrationwascomingfromFanto Motor, soMechanicalteamcheckedthe Fan, itsBearinganditsDamper. Butfound nothingabnormal. Meanwhilesome problemarisesduringfiringinKilnand firingwasstopped. www.systemprotection.in +91-265-2225137

  3. Normally95% ofthetimeMaintenance teamdidn'tcheckRPMandwebelieve whatiswrittenonName-plate. Suchcases posesDangerousriskandSafetytothe OperatorandalsotoEquipment, which motorisdriving, whatinsteadofFanany GearboxwascoupledtotheMotor, the gearboxcouldhavebeendamaged. Sonext timeyouarecheckingaMotororTaking trialofNewMotor, KeepaTachometeror RPMCheckingmeterwithyou. WhenwesharedthiswithmailtoElectrical Fraternityinplants, wefoundthatsimilar typeofproblemfounditinaround19 plants. 1. Therewasacasewherea1500RPM motorwasinstalledinsteadof3000RPM, Somotorwasalwaysgettingoverloaded. Motorratingwas7.5Kw 2. Oneofthecaseifoundwasthatthere was2.2kWveryoldmotor3000RPMwhen replacedwithnew2.2kWenergyefficient 2000RPM. Therewasheavyvibration. ActualrpmofOldmotorwas2750andnew energyefficientmotorwas2950. Inthemeantime, whenProblemofMotor wasgoingon, IthoughttheProblemhas gone "OutofSyllabus" SonothingisoutofSyllabus. Itisjustthe Approach. Hopeitwillhelp, Alsosharewiththeother ElectricalEngineersyouknow. www.systemprotection.in +91-265-2225137

  4. CONTACT INFORMATION 301/2/306, SilverlineComplex,OppositeBBC Tower,Sayajigunj,Vadodara - 390005, Gujarat, India. bdm@systemprotection.in www.systemprotection.in +91-265-2225137

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